Is it morally incorrect to hook up with 2 people at the same time having told one of them that they are exclusively the only one they're hooking up w?

I was in a w2w friends with benefits, however, that wouldn't mean, to me, at least, that either of us could just have sex with whomever we wanted. Those are not my morals and I knew they were also not hers. I'm not one to share myself intimately, sexually or intellectually, with just anyone. It's a very dangerous hurtful game to play with peoples feelings & emotions like that.